Research About Relationship Between BDNF And TRPC3 In A Rat Model Of Alzheimer’s Disease Induced By β-Amyloid Protein

Alzheimer’s disease(AD),is one of the most common chronic degenerative diseases in the central nervous system which is occurring in the elderly.The clinical manifestations are behavior changes,spatial orientation disorder,cognitive dysfunction,personality and behavioral changes and abstract thinking difficulties.Its pathological features are senile plaques(SP)and neurofibrillary tangles(NFT)in the cerebral cortex and hippocampus of patients.There are many hypotheses about the pathogenesis of AD,such as abnormal deposition of β-amyloid protein(Aβ),calcium overload,hyperphosphorylation of Tau protein,etc,among which abnormal deposition of Aβ is dominant,but the specific mechanism of AD is not very clear.Brain derived neurotrophic factor(BDNF)is a member of the neurotrophic factor family(NTFs),which can protect against neurotoxicity and apoptosis caused by(3-amyloid,and safeguard the central nervous system.Canonical transient receptor potential(TRPC)channel is a kind of non-seIective Ca2+ channel,which expresses in the central nervous system abundantly,and related with neuronal survival and apoptosis.The TRPC family consist 7 members(TRPC 1-7),of which TRPC3/6 have similar structures and similar functions.Till now,TRPC3 was thought to play a protective role in neurons,but whether TRPC3 is involved in the pathogenesis of AD and whether BDNF is associated with TRPC3 in AD are still unclear.ObjectiveOligomeric Aβ1-42 lateral ventricle catheter injection is used to make the early Alzheimer’s disease rat model.To investigate whether TRPC3 is involved in the pathogenesis of AD.To investigate whether BDNF play neuronal protection via the TRPC3.This paper may provide new evidences for the AD pathogenesis and new ideas for the prevention and treatment of AD.Methods1.According to experimental requirements,Adaptive feeding 3 days the male Sprague-Dawley rats(SPF grade,5-week old,200-220 g)were randomly divided into AD group/PBS group and AD group/PBS group/AD+BDNF group.2.AD rat models were made by intracerebroventricular injection via catheter of Aβ1-42.BDNF was injected into the lateral ventricle catheter 14 days after modeling.Morphology of Morris water maze was detected 15 days after modeling.3.Using the Morris water maze(MT-200)behavior test(positioning navigation experiments and space exploration experiments)to detect the learning and spatial memory of rats.4.Using RT-PCR(reverse transcription polymerase chain reaction)to detect TRPC1-7 and BDNF mRNA expression of rat hippocampus.5.Using Western blots to detect TRPC3 and BDNF protein expression of rat hippocampus.6.Using Immunohistochemical to detect TRPC3 and BDNF protein expression and localization of rat hippocampus.Results1.Morris water maze behavioral test results showed that compared with the PBS group,the escape latency of the AD group on the fifth day was prolonged[(41.06±4.01)s vs(24.23±4.62)s,n=8,P<0.05].The numbers of platform crossing on the sixth day were decreased[(3.25±0.45)s vs(6.62±0.46)s,n=8,P<0.05].Compared with AD group,the fifth day escape latency of AD+BDNF rats was shortened[(23.30±4.84)s vs(31.06±4.01)s,n=12,P<0.05].The numbers of platform crossing on the sixth day were increased[(5.83±0.75)s vs(3.25±0.45)s,n= 12,P<0,05].2.RT-PCR results showed that TRPC1-7 mRNA(except TRPC2)were expressed in rat hippocampus.Compared with PBS group,the expression of BDNF mRNA in AD group-was decreased[(0.25±0.01)vs(0.35±0.03),n=8,P<0.01],TRPC1/3/4/5/6 mRNA expression were decreased[(0.17 ± 0.03)vs(0.26±0.03),n=8,P<0.05],[(0.06 ± 0.00)vs(0.11 ±0.01),n=8,P<0.05,[(0.28±0.02)vs(0.40±0.03),n=8,P<0.05],[(0.29±0.03)vs(0.47±0.06),n=8,P<0.05],[(0.25±0.03)vs(0.41 ±0.03),n=8,P<0.05].Compared with AD group,the expression of BDNF mRNA was increased in AD+BDNF group[(0.80±0.07)vs(0.52±0.10),n=4,P<0.05],and the expression of TRPC3 mRNA was increased in AD+BDNF group[(0.21±0.05)vs(0.11 ±0.04),n=4,P<0.05].3.Western blotting showed that the expressions of TRPC3 and BDNF protein in the rat hippocampus were decreased in AD rats compared with PBS group[(0.57±0.03)vs(0.81 ±0.02),n=4,P<0.05],[(0.11 ±0.02)vs(0.21 ±0.03),n=4,P<0.05].Compared with AD group,the expressions of TRPC3 and BDNF protein increased in AD+BDNF group[(0.88±0.02)vs(0.57±0.03),n=4,P<0.05],[(0.31 ±0.06)vs(0.11 ±0.02),n=4,P<0.05].4.Immunohistochemistry results showed that TRPC3 was expressed on pyramidal cell membrane and cytoplasm of rat hippocampus,and BDNF was expressed in the cytoplasm.Compared with PBS group rats,TRPC3 and BDNF in AD group had lower staining intensity,the rats tissues of AD+BDNF group had higher staining intensity of TRPC3 and BDNF than AD group.ConclusionThe mRNA and protein expressions of BDNF and TRPC3 were decreased in hippocampus of AD rats.An exogenous BDNF injection appears to improve the spatial learning and memory of AD rats that are impaired by a Aβ1-42 injection,possibly via TRPC3 upregulation and may play a protective role in neurons.